Blomstrand E, Celsing F, Newsholme E A
Department of Biochemistry, University of Oxford, U.K.
Acta Physiol Scand. 1988 May;133(1):115-21. doi: 10.1111/j.1748-1716.1988.tb08388.x.
The plasma concentrations of branched-chain and aromatic amino acids have been measured in two different types of sustained dynamic exercise. Twenty-two subjects participated in the 1986 Stockholm Marathon and eight subjects took part in an army training programme of approximately 1.5-h duration. Both types of exercise caused a significant decrease in the plasma concentration of branched-chain amino acids, while there was no change in the concentration of total (free plus bound to albumin) tryptophan. The plasma concentration of free tryptophan, which was measured in the marathon runners, was found to increase 2.4-fold during the race. This increase is probably caused by a pronounced elevation in the concentration of plasma free fatty acids during exercise, since these are known to displace tryptophan from albumin. The observed increase in plasma free tryptophan concentration, together with the decrease in plasma concentration of branched-chain amino acids, gives rise to a marked increase in the plasma concentration ratio of free tryptophan/branched-chain amino acids. This should lead to an increase in the rate of transport of tryptophan across the blood-brain barrier and hence to an increase in the rate of synthesis of 5-hydroxytryptamine (5-HT) in the brain. An elevated concentration of 5-HT in specific areas of the brain may be responsible, at least in part, for the development of physical, and/or mental fatigue during prolonged exercise.
已在两种不同类型的持续动态运动中测量了支链氨基酸和芳香族氨基酸的血浆浓度。22名受试者参加了1986年的斯德哥尔摩马拉松比赛，8名受试者参加了时长约1.5小时的军事训练项目。两种运动类型均导致支链氨基酸的血浆浓度显著降低，而总（游离加与白蛋白结合）色氨酸的浓度没有变化。在马拉松运动员中测量的游离色氨酸血浆浓度在比赛期间增加了2.4倍。这种增加可能是由于运动期间血浆游离脂肪酸浓度的显著升高所致，因为已知这些游离脂肪酸会将色氨酸从白蛋白上置换下来。观察到的血浆游离色氨酸浓度增加，以及支链氨基酸血浆浓度的降低，导致游离色氨酸/支链氨基酸的血浆浓度比显著增加。这将导致色氨酸穿过血脑屏障的转运速率增加，从而导致大脑中5-羟色胺（5-HT）的合成速率增加。大脑特定区域中5-HT浓度的升高可能至少部分地导致了长时间运动期间身体和/或精神疲劳的产生。
